On Mon, May 18, 2009 at 3:05 PM, Taral wrote:
> Will this do?
>
> (>>=) :: (NFData sa, NFData b) => LI sa -> (sa -> LI b) -> LI b
No, the problem is that >>= on monads has no constraints, it must have the type
> LI a -> (a -> LI b) -> LI b
This is a common problem with trying to use do-notation;
On 19 May 2009, at 09:06, Ryan Ingram wrote:
This is a common problem with trying to use do-notation; there are
some cases where you can't make the object an instance of Monad. The
same problem holds for Data.Set; you'd can write
setBind :: Ord b => Set a -> (a -> Set b) -> Set b
setBind m f
2009/05/18 Miguel Mitrofanov :
> On 19 May 2009, at 09:06, Ryan Ingram wrote:
>
>> This is a common problem with trying to use do-notation; there are
>> some cases where you can't make the object an instance of Monad. The
>> same problem holds for Data.Set; you'd can write
>>
>> setBind :: Ord b =
On Mon, May 18, 2009 at 10:06 PM, Ryan Ingram wrote:
> On Mon, May 18, 2009 at 3:05 PM, Taral wrote:
>> Will this do?
>>
>> (>>=) :: (NFData sa, NFData b) => LI sa -> (sa -> LI b) -> LI b
>
> No, the problem is that >>= on monads has no constraints, it must have the
> type
>> LI a -> (a -> LI b)
To be fair, you can do this with some extensions; I first saw this in
a paper on Oleg's site [1]. Here's some sample code:
{-# LANGUAGE NoImplicitPrelude, TypeFamilies, MultiParamTypeClasses #-}
module SetMonad where
import qualified Data.Set as S
import qualified Prelude as P (Monad, (>>=), (>>)
I've posted it once or twice.
newtype C m r a = C ((a -> m r) -> m r)
It's a monad, regardless of whether m is one or not. If you have something like "return" and "bind", but not exactly the same, you can make
"casting" functions
m a -> C m r a
and backwards.
Jason Dusek wrote on 19.05.2009
Excerpts from Ryan Ingram's message of Tue May 19 10:23:01 +0200 2009:
> To be fair, you can do this with some extensions; I first saw this in
> a paper on Oleg's site [1]. Here's some sample code:
This seems like the same trick as the rmonad package:
http://hackage.haskell.org/cgi-bin/hackage-sc
Minor addition, optimize >>
(I couldn't help myself!)
-- ryan
> instance Ord b => ConstrainedBind (S.Set a) (S.Set b) where
>type BindElem (S.Set a) = a
>m >>= f = S.unions $ map f $ S.toList m
>m >> n = if S.null m then S.empty else n
__
Nicolas Pouillard wrote:
> Excerpts from Ryan Ingram's message of Tue May 19 10:23:01 +0200 2009:
>> To be fair, you can do this with some extensions; I first saw this in
>> a paper on Oleg's site [1]. Here's some sample code:
>
> This seems like the same trick as the rmonad package:
> http://hac
On Tue, May 19, 2009 at 12:54 AM, Miguel Mitrofanov
wrote:
> I've posted it once or twice.
>
> newtype C m r a = C ((a -> m r) -> m r)
>
> It's a monad, regardless of whether m is one or not. If you have something
> like "return" and "bind", but not exactly the same, you can make "casting"
> funct
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